`(2+6x)(3x-5)=0`
`⇔`\(\left[ \begin{array}{l}2+6x=0\\3x-5=0\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}6x=0-2\\3x=0+5\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}6x=-2\\3x=5\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=\dfrac{-2}{6}\\x=\dfrac{5}{3}\end{array} \right.\)
Vậy `S={-2/6;5/3}.`